As we told you this was enormous cutting through oklahoma city and its suburbs with monstrous force. Sam is on the scene. He was there yesterday, there again this morning. Boy, sam, what a massive storm. Yeah, george, we've been on the ground since sunday here in this part of the country and by the way, this will be the fourth day of strong, violent storms that moved through the same part of the country and, yeah, there's going to be more it of today. Watching these storms roll above us right now. We have a little bit of rain but there could be hail and gusty winds and go through all this, you know, with the powerful storms moving through oklahoma again today. Let's do it by the numbers. This massive tornado that touched down here touched down in the afternoon in new castle, roared all the way toward moore damaging on its way. It was a monster tornado. We don't have the official estimates yet but we can only go by the eyewitness accounts that this storm was about a mile wide, terrifying as it moved toward this town, a town that had the same situation happen in 1999. Oh, my god. That thing is huge. That is huge. Reporter: At 2:40 in the afternoon the tornado warning was sent to the residents of moore, oklahoma, to take cover immediately. This is a tornado emergency. Oh, my god. Now it's on the ground. That's on the ground. A tornado. Reporter:16 minces later the estimated mile wide tornado touches down, just as students are getting ready to be dismissed for the day. Stop it now. Stop it now. Reporter: Estimated the strength of an ef-4 twister with winds of almost 200 miles an hour it tears through the new castle/moore area for a gut-wrenching 40 minutes damaging those schools and leveling homes. Some catching fire. It's ripping up everything in its path. Reporter: At 3:36 it dissertd dissipates and the hunt for survivors begins. Her car looks like it's been run through a meat grinder. Reporter: It tore a 1-mile gash in the earth destroying what used to be the oklahoma city suburbs. Oh, my gosh, I don't know if people lived in that one. I honestly do not know if people lived in that. Reporter: Just moments after the twister passes helicopters capture survivors emerging to find their homes destroyed. And rescuers working frantically digging through debris to find others. We were pulling walls off of people. There were people crawling out from anywhere and everywhere. Basically just a war zone. Reporter: Blocks and blocks of neighborhoods reduced to smoking piles of wood and brick. Cars twisted into mangled heaps. Overnight the streets are covered in dark, wet debris as officers try to control the chaos. It's nighttime in moore and there's been a steady stream of emergency vehicles coming right down which is south much west fourth street. This is, by the way, right over there if we turn the camera there, that's the moore medical center that was so badly damaged in this storm. This morning, the numbers are devastating and heartbreaking. Rescue crews go door to door making sure no one is still trapped beneath the rubble. Additional national guard members have been deployed by oklahoma governor mary fallin. This is going to be so difficult today. There is a fourth day of these powerful storms and folks are just trying to clean up and find out what's left in moore. Let's get to the boards and show you why it happened in the first place much the pattern, classic for may and, yes, we've had a quiet tornado season but this is the pattern that delivers the big storms and tornadoes. All that air rushing up, cold clashing against it coming out of canada being fueled by the jet stream. The jet stream grabs those storms and jump those up to incredible heights and give room for these towering storms to develop that can carry tornadoes. Catch this from texas all the way north where. We're a little concerned, dallas, ft. Worth, arlington to waco, tyler, even into shreveport an area of concern for these powerful storms. Robin.

This transcript has been automatically generated and may not be 100% accurate.

Now Playing: Body Cameras Shine Spotlight on Police

Now Playing: Shayna Hubers Says She was the Victim of Domestic Violence

Now Playing: California Wildfires Lead Governor to Declare a State of Emergency